1. Field of the Invention
The present invention relates to a segment for lining cavities, in particular tunnels, which includes a substantially shell-shaped body bounded by an inner face, an outer face, and side faces, the latter exhibiting at least one opening for receiving a dowel.
2. The Prior Art
A frequently used technique in lining tunnels, shafts, etc., is tubbing. Individual tubbing segments are conveyed into the newly excavated tunnel where they are assembled to form a complete lining. To speed up installation and automatize the lining process, there is an increased use of tubbing segments with which an interlocking connection can be established between adjacent segments. Such a connection is often achieved by a dowel penetrating into a suitable bore in the adjacent segment.
A problem with connections of this kind is that, due to tolerances, measuring errors, etc., it will not always be possible to build or install the individual segments in such a way that the dowels are precisely aligned with the corresponding holes. For this reason allowances should be made for a certain radial displacement between the axis of the dowel and that of the bore into which the dowel is to be fitted, without any functional impairment.
In CH-A 654066 tunnel segments are disclosed which are joined by dowels. Different dowel variants are proposed which are to prevent the segments from falling apart once they have been fastened together. In order to avoid any damage while the dowels are being inserted into their openings, partially funnel-shaped elements are provided to facilitate assembly and prevent the holes and dowels from being damaged during fitting. There are no tolerances for compensating inaccuracies in the assembled state, however. As a consequence, problems are encountered with such segments in certain applications.
EP-A 100 771 describes an invention for connecting segments which is concerned with the above problem. The known connecting means substantially comprise sleeves into which the dowels are inserted so as to provide a force-mediated connection. To allow for variations in radial direction, the dowel sleeves are conical at their open ends, such that the dowels can undergo deformations in this area. This implies that the dowels must be made soft and flexible enough to permit such deformations. As a consequence, a large number of dowels are required to achieve a predetermined holding force. Moreover, this solution does not permit simple manufacture of the dowels, by pouring them as concrete elements integral with the body of the respective segment, for instance. It has further been found that the comparatively thin dowels of this type of construction frequently break upon insertion, thus leading to losses of material and delays in the lining process.
In DE-A 22 38 792 a tunnel lining is described in which the dowel holes are provided with spring rings. Such rings provide for a certain radial adjustment to compensate manufacturing tolerances. However, due to the spring characteristics and the essentially point-type contact between spring ring and dowel, the latter cannot be anchored securely in the segment.
Other solutions are disclosed in FR-A 78 25 472 and in DE-A 20 27 149. None of these solutions have proved completely satisfactory in practical use, however.
It is an object of the present invention to provide a segment of the above type which is easy to manufacture and to handle, and which offers a compensation in the instance of displacements in radial direction of the dowel.
In the invention this object is achieved by configuring the opening as a substantially cylindrical bore into which projects a tube of limited deformability, a gap being provided between the outer circumference of the tube and the wall of the bore.
An essential characteristic of the invention is the special configuration of the opening receiving the dowel. In principle, the invention is suited for assemblies of segments where any two segments to be fastened together are provided with corresponding openings, and where before installation a separately manufactured dowel is driven into one of these openings. According to the invention one of the two openings or both openings may be configured as specified in the invention. Moreover, one of the segments to be connected may include dowels which are moulded integral therewith and which are driven into the appropriately configured openings of the corresponding segment. It is a special advantage of the present invention that the dowel may be designed to suit any special requirements, and particularly, that the dowel may be made completely rigid.
On account of the substantially plastic deformation of the tube, the dowel will be anchored securely once the segments have been connected. Another advantage is that any movement of the tube in radial direction is limited by the wall of the bore, thus preventing any breaking or other damage even in the instance of faulty handling.
Manufacture of a segment of the invention is facilitated by placing a deformable material in the gap between bore and tube. During manufacture the deformable material acts as a lost casing, which will reduce production efforts and costs significantly.
Insertion of the dowel is facilitated by providing that the tube preferably end flush with the side face of the segment, its opening being flared in this area.
Satisfactory deformation of the tube may further be ensured by configuring the tube as a steel element which is embedded in the body of the segment, the depth of the bore exceeding the envisaged penetration depth of the dowel by at least 10 percent, and preferably by at least 20 percent, of the tube diameter. Special preference is given to a variant in which the gap has a width of 5 to 20 percent of the tube diameter.
The present invention is further concerned with an assembly of segments of the type described above, and a segment to be fastened thereto, which is provided with at least one dowel moulded integral with the body. As a result, a particularly stable connection is produced in a simple and cost-effective way.
A further advantage is gained by configuring the segments such that the dowel is provided substantially in one piece with and of the same material as the body of the segment. In this manner an interlocking connection is established utilizing the strength of the basic material. The manufacturing process itself is kept simple in this instance. A further increase in strength is achieved by providing reinforcing elements which extend from the body into the dowel.